High strength and toughness steel composition and machine parts made therewith

ABSTRACT

A mud pump with components manufactured from high strength and toughness steel is disclosed. The mud pump includes a power end and a fluid end. The power end includes a motor, crankshaft rotationally engaged with the motor and a connecting rod rotationally engaged with the crank shaft. The fluid end is operatively connected to the power end and includes a piston, a cylinder configured to operatively engage the plunger, and a drilling fluid module. The crankshaft, the connecting rod, the piston, and the cylinder may each be fabricated from a high strength and toughness steel composition having the following composition in weight percent: 0.25-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.80% silicon, 1.40-2.00% chromium, 0.10-0.55% molybdenum, a maximum of 0.040% aluminum, a maximum of 0.025% phosphorous, a maximum of 0.20% sulfur, a balance of iron, and incidental impurities.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part pursuant to 35 U.S.C. § 120 of U.S. patent application Ser. No. 16/251,469 filed Jan. 18, 2019, which itself is a continuation-in-part pursuant to 35 U.S.C. § 120 of U.S. patent application Ser. No. 14/998,669 filed Feb. 1, 2016.

FIELD OF THE DISCLOSURE

This disclosure generally relates to high strength and toughness steel compositions and, more particularly, to fabricated machine parts made from said high strength and toughness steel.

BACKGROUND OF THE DISCLOSURE

In the modern world, there is ever increasing demand for products derived from oil retrieved from deep within the earth. An oil well is a boring into the ground that is designed to bring petroleum oil hydrocarbons to the surface. The well is created by drilling a hole with a drilling rig that rotates a drill string with a bit attached. Drilling fluid also known as drilling mud is an essential element to creating the wellbore. The drilling fluid is pumped into the wellbore down the drill pipe and exits the drill bit at high pressure. The drilling fluid then circulates back to the surface through a space between the drill pipe and the outer surface of the well called the annulus, conveying cut rock with it. This process requires a reciprocating pump known as a mud pump.

The mud pump or drilling pump circulates the drilling mud downhole during drilling operations. The drilling mud is pumped downhole at pressures up to 7500 psi through the drill string and returns back to the surface via the well's annulus. This drilling mud circulation process performs numerous critical functions which include cooling the drill bit, cleaning the well bore of drill cuttings and providing hydrostatic pressure to prevent formation fluids from entering into the well bore.

Mud pumps are typically positive displacement, reciprocating pumps that are comprised of a power-end and fluid-end assembly. The power end includes a motor and a crankshaft rotationally engaged with the motor. Moreover, the power end may include a connection rod rotationally engaged with the crankshaft. The power-end converts the rotation of the crank shaft to a reciprocating motion by using a crosshead guide while the fluid-end utilizes this reciprocating action to achieve the function of pumping the pressurized mud. The fluid-end assembly is comprised of drilling fluid modules, cylinders, pistons, and valves. Many of the fluid-end assembly components are high-wear items. A key and necessary feature of a drilling pump is its ability to provide a constant flow rate of fluid at a specific pressure. Over the past century, numerous mud pump design configurations have been introduced but the most common designs on the market today are duplex, triplex, and quintuplex models.

Because the mud pump serves so many critical functions, drilling cannot take place without an operational mud pump. Production downtime can equate to hundreds of thousands of lost dollars per day. Ensuring minimal downtime of production machinery and other critical equipment is essential. Manufacturing critical parts out of alloys with high strength and toughness can increase the service life of these components and minimize downtime of crucial equipment.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the present disclosure, a mud pump is disclosed. The mud pump includes a power end and a fluid end. The power end includes a motor, a crankshaft rotationally engaged with the motor and a connecting rod rotationally engaged with the crank shaft. The fluid end is operatively connected to the power end and includes a piston, a cylinder configured to operatively engage the plunger, and drilling fluid module. The crank shaft, connecting rod, piston, cylinder, and other components may each be fabricated from a high strength and toughness steel composition having the following composition in percent by weight: 0.25-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.80% silicon, 1.40-2.00% chromium, 0.10-0.55% molybdenum, a maximum of 0.040% aluminum, a maximum of 0.025% phosphorous, a maximum of 0.20% sulfur, a balance of iron, and incidental impurities.

In accordance with another aspect of the present disclosure, a fabricated machine part is disclosed. The machine part is manufactured from a steel composition having the following composition in percent by weight: 0.25-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.80% silicon, 1.40-2.00% chromium, 0.10-0.55% molybdenum, a maximum of 0.040% aluminum, a maximum of 0.025% phosphorous, a maximum of 0.20% sulfur, a balance of iron, and incidental impurities.

In yet another aspect of the present disclosure, a steel composition is disclosed. The steel composition may have the following composition in percent by weight: 0.25-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.80% silicon, 1.40-2.00% chromium, 0.10-0.55% molybdenum, a maximum of 0.040% aluminum, a maximum of 0.025% phosphorous, a maximum of 0.20% sulfur, a balance of iron, and incidental impurities.

These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of an exemplary mud pump, constructed in accordance with the present disclosure.

FIG. 2 is a flowchart of a series of steps that may be involved in manufacturing machine parts from high strength and toughness steel in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to FIG. 1, a side cross-sectional view of the exemplary mud pump 100 manufactured in accordance with the present disclosure is depicted. As represented therein, the mud pump 100 may include a power end 110 and a fluid end 120. The power end 110 is configured to provide work to the fluid end 120 thereby allowing the fluid end 120 to pump pressurized drilling mud into a wellbore. The power end 110 includes a motor (not shown) and a power end housing 130 which surrounds a main gear 140, crankshaft 150, and connecting rod 160. The crankshaft 150 is rotationally engaged with the motor via the main gear 140, and the connecting rod 160 is further rotationally engaged with the crankshaft 150. The connecting rod connects to an extension rod 170 in a crosshead guide 180. As the motor causes the main gear 140 to rotate, the crankshaft 150 rotates and causes the connecting rod 160 to move within the crosshead guide 180. This moves the extension rod 170 back and forth along a longitudinal axis of the pump 100. The extension rod 170 operatively connects the power end to the fluid end.

The fluid end 120 includes a fluid housing 190 at least partially surrounding the extension rod 170, a piston 200, a cylinder 210 and a drilling fluid module 220. The extension rod 170 is connected to the piston 200 and causes the piston 200 to move within the cylinder 210. While the current disclosure and drawings discuss a cylinder 210 and piston 200 arrangement, the current disclosure may also encompass an alternate cylinder and plunger arrangement. Accordingly, it is to be understood that the piston may be replaced by a plunger without departure from the scope of the current disclosure.

The drilling fluid module 220 is proximate the cylinder 210 and defines a flow passage 230 which may be pressurized and depressurized by the reciprocation of the piston 200 within the cylinder 210. As the piston 200 moves away from the drilling fluid module 220, drilling mud is drawn into the flow passage 230 through an inlet valve 240. As the piston moves towards the drilling fluid module 220, the drilling mud contained within the flow passage 230 is moved under pressure through an outlet valve 250 and to a wellbore. Once in the wellbore, the drilling mud serves to cool and lubricate the drill bit, clean the well bore of drill cuttings and provide hydrostatic pressure to prevent formation fluids from entering into the wellbore.

Although the illustrated cross section shows only a single crankshaft, piston, and drilling fluid module, most mud pumps include 2-6 multiples of the described system driven by a single motor. These pumps (duplex, triplex, quintuplex etc.) provide a more consistent pressure to the wellbore. However, they also require correspondingly more components which suffer wear and must be replaced.

Because mud pumps must run continuously for extended periods, its components are subject to high stress. In order to avoid expensive downtime, these components must be made from high strength and toughness steel compositions such as that described below. The same high strength and toughness may also be of benefit for use in components for other oil exploration machinery and general industrial machinery components.

The following composition of high strength and toughness steel may be used for any fabricated components which require high strength and toughness, including cylinders, pistons, plungers, crankshafts, gears, and similar machine parts. All percentages below are percent by weight.

Carbon 0.25-0.55% Manganese 0.70-1.50% Silicon 0.80% max. Chromium 1.40-2.00% Molybdenum 0.10-0.55% Aluminum 0.040% max. Phosphorous 0.025% max. Sulfur 0.20% max. Iron balance, and Incidental impurities.

For components for which toughness is more critical than strength, the following composition with narrowed ranges within the above described composition may be used. All percentages describe percent by weight.

Carbon 0.30-0.50% Manganese 1.05-1.45% Silicon 0.60% max. Chromium 1.50-2.00% Molybdenum 0.10-0.45% Aluminum 0.035% max. Phosphorous 0.020% max. Sulfur .0.015% max. Iron balance, and Incidental impurities.

For components for which toughness is most critical, the following composition with narrowed ranges within the above described compositions may be used. All percentages describe percent by weight.

Carbon 0.35-0.45% Manganese 1.15-1.35% Silicon 0.40% max. Chromium 1.50-1.90% Molybdenum 0.10-0.30% Aluminum 0.030% max. Phosphorous 0.015% max. Sulfur 0.003% max. Iron balance, and Incidental impurities.

Carbon is necessary to provide the required hardness and wear resistance. If carbon is significantly higher than 0.55% by weight, the mold block will exhibit low machinability and polishing characteristics. Preferably, a maximum of 0.50% by weight carbon is used to ensure good machinability. If substantially less than 0.25% by weight carbon is used, wear resistance and mechanical properties will not be suitable for service conditions to which the mold blocks are subjected. Preferably, a minimum of 0.30% by weight carbon is used to ensure acceptable wear resistance, hardness, and mechanical properties. Most preferably, carbon in the range of 0.35% to 0.45% by weight with an aim of 0.40% should be used.

Manganese is essential for hardenability and as a deoxidizer in the steelmaking process. It also acts to control sulphides in forging operations. In combination with the other alloying elements, if significantly higher than 1.50% by weight is present, there is a risk that retained austenite will be present. If substantially less than 0.70% by weight manganese is present, the hardenability of the fabricated component will be lessened. In addition, to ensure sulfur control, the manganese content should be present in an amount of at least 20 times the sulfur content. Manganese also contributes to wear resistance, although to a lesser extent than other carbide formers. Preferably manganese will be present in the range of 1.05% to 1.45% by weight, and most preferably from 1.15% to 1.35% by weight.

Silicon is specified for its deoxidizing ability in the steelmaking process. If present in substantially greater quantities than 0.80% by weight, there will be a predisposition towards embrittlement of the final product.

Chromium is necessary for carbide formation, for hardenability and for wear resistance. If substantially more than the maximum of 2.00% by weight chromium is present, the hardening temperature would be too high for normal production heat treatment process. Below the specified minimum of 1.40% by weight chromium, the wear resistance will be negatively affected. Preferably, chromium is present in the amount of 1.50% to 2.00% by weight, and most preferably from 1.50% to 1.90% by weight.

Molybdenum is a key element contributing to hardenability and wear resistance by the fact that it is a strong carbide former. It is beneficial effects are effective in the range of 0.10% to 0.55% by weight, but preferably it is maintained in the lower band of the range from 0.10% to 0.45% by weight, and most preferably in the range of 0.10% to 0.30% by weight.

Aluminum is desirable for grain refinement but can have a detrimental effect on steel quality by causing the presence of aluminates, an undesirable impurity. It is therefore important to minimize the addition of aluminum to a maximum of 0.040% by weight in the final melt composition. Most preferably an aim of 0.020% by weight aluminum will achieve grain refinement.

Phosphorus can increase machinability but the detrimental effects of this element in tool steels, such as an increase in ductile-brittle transition temperature, outweigh any beneficial effects. Accordingly, the phosphorus content should not be more than the specified maximum of 0.025% by weight,

Sulfur is a key element for machinability and it is commonly believed that a content higher than 0.045% in tool steel will result in acceptable machinability. However, to maintain control of sulfides during processing will be necessary to avoid a content over 0.20% by weight sulfur, preferably lower than 0.015% by weight, and most preferably lower than 0.003% by weight.

In all the described compositions, the balance of the steel is made up of iron. Some incidental impurities may also be present. In order to exhibit the required operating characteristics described above, the final composition should be water quenched.

Referring now to FIG. 2, a method of manufacturing blocks of the steel composition for manufacture of components is as follows:

A melt of steel is prepared in an electric arc furnace by:

-   -   a. melting the bulk of the steel composition containing a         majority of the alloy ingredients to produce a steel melt         suitable for tapping into a receptacle (block 502),     -   b. thereafter heating, alloying, and refining the heat to bring         the heat to its final composition (block 504),     -   c. vacuum degassing, teeming, and casting the gear by bottom         pouring practices to form ingots (block 506),     -   d. hot working the ingots to form a mud pump component,         fabricated machine part, or block (block 508), and     -   e. thereafter heat treating the mud pump component, fabricated         machine part, or block by water quenching and tempering to form         a final hot work product (block 510).

It will be understood that after processing the steel in the manner described above, the final hot worked product should be subjected to austenitizing at a temperature of between 800° and 900° C. (block 512), quenching in water (block 514), and tempering at a temperature of between 500° and 700° C. (block 516). Following said treatment, the resultant product will exhibit a microstructure comprising mostly bainite and possibly a mixture of bainite and perlite which will be deeper than ¼ of the thickness of the block. 

What is claimed is:
 1. A mud pump, comprising: a power end having a motor, a crankshaft rotationally engaged with the motor, and a connecting rod rotationally engaged with the crankshaft; and a fluid end operatively connected to the power end and having a piston, a cylinder configured to operatively engage the plunger, and a drilling fluid module, the crankshaft, the connecting rod, the piston, and the cylinder each being made of a steel composition having the following composition in percent by weight: C 0.25-0.55%, Mn 0.70-1.50%, Si 0.80% max., Cr 1.40-2.00%, Mo 0.10-0.55%, Al 0.040% max., P 0.025% max., S 0.20% max., Fe balance, and incidental impurities.


2. The mud pump of claim 1, wherein the steel composition comprises the following composition in percent by weight: C 0.30-0.50%, Mn 1.05-1.45%, Si 0.60% max., Cr 1.50-2.00%, Mo 0.10-0.45%, Al 0.035% max., P 0.020% max., S 0.15% max., Fe balance, and incidental impurities.


3. The mud pump of claim 1, wherein the steel composition comprises the following composition in percent by weight: C 0.35-0.45%, Mn 1.15-1.35%, Si 0.40% max., Cr 1.50-1.90%, Mo 0.10-0.30%, Al 0.030% max., P 0.015% max., S 0.003% max., Fe balance, and incidental impurities.


4. The mud pump of claim 1, wherein a mud pump component made of the steel composition is prepared in an electric arc furnace by: a. melting the bulk of the steel composition containing the majority of the alloy ingredients to produce a steel melt suitable for tapping into a receptacle, b. thereafter tapping, heating, alloying, and refining the heat to bring the heat to its final composition, c. vacuum degassing, teeming and casting the heat by bottom pouring practices to form an ingot, d. hot working the ingot to form a mud pump component, and e. thereafter heat treating the mud pump component by water quenching and tempering to form a final hot work product.
 5. The mud pump of claim 5, wherein the final hot work product is subsequently subjected to: austenitizing at a temperature of between 800° and 900° C., quenching in water, and tempering at a temperature of between 500° and 700° C. to form a microstructure consisting mostly of bainite or a mixture of bainite and perlite which will be deeper than ¼ of the thickness of the block.
 6. A fabricated machine part manufactured from a steel composition having the following composition in percent by weight: C 0.25-0.55%, Mn 0.70-1.50%, Si 0.80% max., Cr 1.40-2.00%, Mo 0.10-0.55%, Al 0.040% max., P 0.025% max., S 0.20% max., Fe balance, and incidental impurities.


7. The machine part of claim 6, wherein the steel composition comprises the following composition in percent by weight: C 0.30-0.50%, Mn 1.05-1.45%, Si 0.60% max., Cr 1.50-2.00%, Mo 0.10-0.45%, Al 0.035% max., P 0.020% max., S 0.15% max., Fe balance, and incidental impurities.


8. The machine part of claim 6, wherein the steel composition comprises the following composition in percent by weight: C 0.35-0.45%, Mn 1.15-1.35%, Si 0.40% max., Cr 1.50-1.90%, Mo 0.10-0.30%, Al 0.030% max., P 0.015% max., S 0.003% max., Fe balance, and incidental impurities.


9. The machine part of claim 6, wherein a fabricated machine part made of the steel composition is prepared from a melt of steel prepared in an electric arc furnace by: a. melting the bulk of the steel composition containing the majority of the alloy ingredients to produce a steel melt suitable for tapping into a receptacle, b. thereafter tapping, heating, alloying, and refining the heat to bring the heat to its final composition, c. vacuum degassing, teeming and casting the heat by bottom pouring practices to form an ingot, d. hot working the ingot to form a fabricated machine part, and e. thereafter heat treating the fabricated machine part by water quenching and tempering to form a final hot work product.
 10. The machine part of claim 9, wherein the final hot work product is subsequently subjected to: austenitizing at a temperature of between 800° and 900° C., quenching in water, and tempering at a temperature of between 500° and 700° C. to form a microstructure consisting mostly of bainite or a mixture of bainite and perlite which will be deeper than ¼ of the thickness of the block.
 11. The machine part of claim 6, wherein the machine part is a crankshaft.
 12. The machine part of claim 6, wherein the machine part is a piston.
 13. The machine part of claim 6, wherein the machine part is a gear.
 14. The machine part of claim 6, wherein the machine part is a component of oil field exploration machinery.
 15. The machine part of claim 6, wherein the machine part is a component of a mud pump.
 16. A steel comprising the following composition in percent by weight: C 0.25-0.55%, Mn 0.70-1.50%, Si 0.80% max., Cr 1.40-2.00%, Mo 0.10-0.55%, Al 0.040% max., P 0.025% max., S 0.20% max., Fe balance, and incidental impurities.


17. The steel of claim 16, wherein the steel composition comprises the following composition in percent by weight: C 0.30-0.50%, Mn 1.05-1.45%, Si 0.60% max., Cr 1.50-2.00%, Mo 0.10-0.45%, Al 0.035% max., P 0.020% max., S 0.15% max., Fe balance, and incidental impurities.


18. The steel of claim 16, wherein the steel composition comprises the following composition in percent by weight: C 0.35-0.45%, Mn 1.15-1.35%, Si 0.40% max., Cr 1.50-1.90%, Mo 0.10-0.30%, Al 0.030% max., P 0.015% max., S 0.003% max., Fe balance, and incidental impurities.


19. The steel of claim 16, wherein a block of the steel composition is prepared in an electric arc furnace by: a. melting the bulk of the steel composition containing the majority of the alloy ingredients to produce a steel melt suitable for tapping into a receptacle, b. thereafter tapping, heating, alloying, and refining the heat to bring the heat to its final composition, c. vacuum degassing, teeming and casting the heat by bottom pouring practices to form an ingot, d. hot working the ingot to form a block, and e. thereafter heat treating the block by water quenching and tempering to form a final hot work product.
 20. The steel of claim 19, wherein the final hot work product is subsequently subjected to: austenitizing at a temperature of between 800° and 900° C., quenching in water, and tempering at a temperature of between 500° and 700° C. to form a microstructure consisting mostly of bainite or a mixture of bainite and perlite which will be deeper than ¼ of the thickness of the block. 